<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Title</title>
    <style>
        *{
            padding:0;
            margin:0;
        }
        #root{
            width:375px;
            height:100px;
            background: green;
        }
        #one{
            width:187.5px;
            height:100px;
            background: red;
        }
        #two{
            width:50%;
            height:100px;
            background: pink;
        }
    </style>
</head>
<body>
    <div id="root"></div>
    <div id="one"></div>
    <div id="two"></div>
</body>
<script>
    // 414   207
    // "width=device-width, initial-scale=2"
    // initial-scale=1.0   设备独立像素/布局视口
    // 414/828=0.5;
  console.log("布局视口",document.documentElement.clientWidth);
  console.log("视觉视口",window.innerWidth);
</script>
</html>